Oil burner



March 2, 1943. I w. F. 'KLOCKAU OIL BURNER Filed Aug. 2, .1939

2 Sheets-Shut 1 I I I 211151- MZ/zbm zfficzau' March 2, 1943. w. F.KLOCKAU on, BURNER Filed Aug. 2, 1939 WW da n Patented Mar. 2, 1943UNITED STATES PATENT OFFICE OIL BURNER William F. Klockau, Moline, Ill.

Application August 2, 1939', Serial No. 287,873

12 Claims.

The present invention relates to oil burners, and has particularreference to the provision of improved means for thermally insulatingthe burner nozzle from heat radiated from the flame and the combustionchamber.

For a considerable time, manufacturers of boilers and furnaces have beenendeavoring to develop successful heating units of relatively smallsize, i. e., in the neighborhood of 80,000 B, t. u. output, in which oilis used for fuel. The principal difficulty encountered in thedevelopment of these small heating units is that of obtaining a burnerwhich can successfully burn oil at a rate low enough to overcome highstack losses. Heretofore, there have been very few burners, if any,capable of giving satisfactory performance when using nozzles of suchsmall capacity as approximately one gallon per hour, and even theseburners usually produce too much heat for many of the smaller heatingunits to absorb eificiently.

There is a considerable demand for small heating units of theapproximate size above mentioned, owing to the large number of smallfour and five room homes being built at the present time. For example,an oil burner that can successfully burn oil at a rate as low as gallonper hour would fill an immediate need. It is well known, of course, thatvaporizing burners and low pressure burners are now available inrelatively small sizes. However, the vaporizing burners areunsatisfactory inasmuch as they require a light grade, high priced fueland are difiicult to operate automatically. The low pressure burners aretoo noisy in their operation, and are relatively expensive tomanufacture. Contrasted to these, the high pressure burner is the mostdesirable or the only practical type of burner now known as havingdefinite potentialities for this market. This type of burner is low incost, quiet in operation, requires little service, and uses the heaviestgrades of domestic fuel oil.

The principal difficulty experienced with pressure type oil burnersusing nozzles of very small capacity has been the clogging of thenozzles, owing to the extremely fine passages necessary to keep the fueldelivery rate low enough at atomizing pressures. For example, the slotsin a typical one-gallon per hour nozzle are approximately .008 inchwide. Screens and filters that will screen out particles much smallerthan .008 inch in diameter have been used in conjunction with theseone-gallon per hour nozzles, but such nozzles are still subject toclogging, and must be cleanedat frequent intervals. Under all but themost extremely favorable conditions, these intervals are so short thatsuch nozzles have generally been deemed impractical, at least forordinary operating conditions.

From the fact that the use of filters of smaller screening size than thesize of the nozzle slots and orifice does not avoid this frequentclogging of the slots, it follows that this clogging is not due tosediment or particles suspended in the oil. I have determined byconclusive experiments that this frequent clogging of extremely smallcapacity nozzles is due to high temperatures, particularly the action ofradiant heat from the combustion space impinging on the nozzle. Fuel oilis a compound of hydrocarbons of a complex nature, whose molecules aredistilled off by heat. Some molecules pass off at relatively lowtemperatures, and as the temperature rises more and more pass off.Finally, a temperature is reached (in the neighborhood of 680 F.) whereno more evaporation takes place, but a sticky tar-like substanceremains. A very small deposit of this substance will interfere with theproper spraying action of the nozzle, or will clog it up entirely.

Moreover, it is not necessary for the nozzle to attain a temperature of680 F. to cause it to clog. If only 40% or 50% of the oil remaining inthe nozzle is distilled off, the remaining oil is of a consistency thatwill be very difficult to expel when the burner again resumes operation.Gradually, a mass of material accumulates in the nozzle until cloggingoccurs. It must be borne in mind that only a very minute quantity of oilremains in the nozzle passages after a burner stops operating, and thatdistillation takes place very rapidly. Furthermore, at temperatures aslow as 200 F. the liquid oil will be driven off, while solids andsemi-fluid residues will remain in the nozzle passages. A small quantityof this material is deposited after each burner operation, until finallythe nozzle clogs.

By placing a small thermocouple tightly against the nozzle tip, I havemade accurate temperature measurements of the nozzle during burneroperations and immediately following cessation of burner operation.These tests show that the nozzle begins to heat up very rapidly afterthe burner is started, notwithstanding the fact that cold air is beingpassed over the burner at a relatively high velocity, and cold oil isbeing passed through it. The temperature rise is due to the absorptionof radiant heat from the flame and adjacent refractory and metallicparts. Numerous tests were made on various types of boilers andfurnaces, as well as with different designs of combustion chambers andcombustion chamber material, during which the rate of temperature rise,and the maximum temperature reached, varied under different conditions.The lowest maximum temperature recorded while the burner was inoperation was 260 F., while the highest was 490 F. Maximum temperaturewas attained in from ten to fifteen minutes of operation from a coldstart, depending upon conditions. Immediately after stopping the burner,the temperature usually rises about ten degrees F. and then slowlydrops. After thirty minutes or so it comes down to about 150 F.

The foregoing observations and experiments have demonstrated to me theimportance of shielding the nozzle tip from the radiant heat of j theflame while the burner is in operation, and also of shielding the nozzletip from the radiant heat of the combustion chamber after the burner hasstopped. To the attainment of these ends, I V

have devised different forms of improved heat shields for the burnernozzle, which I shall now describe in connection with the accompanyingdrawings. In these drawings:

Figure 1 is an axial sectional View through a conventional design ofburner of the type described above, illustrating one embodiment of myimproved heat shield;

Figure 2 is a perspective view of this heat shield;

Figure 3 is a fragmentary view similar to Figure 1, showing anotherembodiment of my improved heat shield;

Figures 4 and 5 are front elevational and sectional views, respectively,on a larger scale, of the nozzle shield illustrated in Figure 3;

Figure 6 is an axial sectional view through a conventional burner,illustrating my invention embodied in the form of a combination nozzleshield and electrode bracket;

Figure '7 is a transverse sectional view taken approximately on theplane of the line 'i-'l of Figure 6, and

Figure 8 is a fragmentary sectional view similar to Figure 6 but showingthe use of a difierent form of nozzle shield, similar to thatillustrated in Figure 3.

One of the refractory enclosing Walls of the combustion chamber isindicated at 52. Enter ing the combustion chamber through this wall isthe abovedescribed type of burner assembly comprising a draft tube idfor the air supply, and an oil pipe I6 for the fuel supply. The innerend of the draft tube [4 is usually provided with an air deflector ringwhich is fastened to or formed integral with the draft tube. Thisdeflector ring serves to constrict the air stream to a high velocitytaperin jet converging toward a point beyond the nozzle head. Ashereinafter described in connection with Figure 3, this deflector ringmay be provided with inclined vanes for imparting a helical or spiral.twist to the air stream. Secured to the innerend of the oil pipe I5 isthe nozzle body IT. The nozzle tip l8 at the inner end of this body isprovided with a relatively small central orifice I9. The slots orpassageways which determine the capacity of the burner are usuallylocated in the body of the nozzle, anterior to this discharge orificeE3. The draft tube I4 is usually connected to receive air under pressurefrom a displacement blower, turbo blower, fan or the like. The oil pipei6 is usually connected to receive fuel oil under pressure from V a gearpump, pressure chamber, or other source Ignition is usually effected ofpressure feed. electrically in these burners by a spark drawn betweentwo electrodes 22 disposed slightly beyond and above the nozzle tip l8.These electrodes are mounted in sleeves 23 of porcelain or othersuitable insulating material which are clamped in the arms of asupporting spider 24. The spider clamps about the oil pipe l6, andcomprises three equidistantly spaced arms 2 ia2-'ia and 242) whichextend radially outwardly into proximity to the inner surface of thedraft tube l4, thereby centering the oil pipe within the draft tube. Thetwo spider arms 24a-24a are of split clamping construction adapted toclamp over the insulating sleeves 23 of the electrodes.

The embodiment of heat shield illustrated in Figures 1 and 2 is of areadily attachable and detachable design adapted for widespread use onvarious constructions of burners now on the --market, withoutnecessitating any change in the burner construction. 'In thisembodiment, the shield, designated 21 in its entirety, is in the form ofa semi-spherical or dome-shapedmember 23 having an arm 29 extendingrearwardly from the edge of the member 28, which armis formed with aU-shaped clamp 39 at its inner end. An aperture 3| located centrally inthe semi-spherical cap portion 28 is adapted to align with the jetorifice IS in the nozzle tip. The entire unit can be readily formed asva sheet metal stamping, or can be cast,.as desired. I prefer toconstruct it as a stainless steel stamping, and to give a high polish tothe outer surface of the spherical cap portion 28 for reflecting amaximum amount of the radiant heatimpinging nozzle tip it so as to leavean air space 33 be- V tween the shield and tip. .A relatively rapid flowof air passes through this space 33 .and out through the aperture 3| inthe shield, this flow of air resulting from the forced draftthrough thedraft tube I 4, and also from the aspirating action of the fuel nozzle,the airflow exerting a cooling influence on the nozzle tip and also onthe inner surface of the heatshield. It will'be seen from the foregoingthatmy improvedshield will thermally insulate the nozzle tip from ra-'diant heat emanating from thefiameduring burner operation, and will alsoact as a thermal barrier against the radiant heat of the combustionchamber afterrthe burnerhas ceased operating. During the running period,the ,high speed air flow impelled through the passageway 33 by theforced draft and by the ,aspirating action of the nozzleexerts .asubstantial cooling effect on the nozzle tip, shield 28, arm 29,.clamp30, etc., and duringthe non-running periodari air flow is also impelledthrough this passageway 33 byreason of the natural draft through thecombustion chamber. This air flow prevents convection heat fromreaching'the. nozzl'ejtip. If desired, the supporting arm portion 29.01?the shield may be made somewhat longer, so that the spring-clamp portion33. can be engaged over. the ,oil pipe 16 instead of overQthenozz'lehead. a

In Figures 3, 4 and 5, I have illustrated a modified construction ofheatlshield in lwhich Qa relatively large aggregate area of opening iseffective in the outer portion of the shield for the circulation of aconsiderable amount of air therethrough, but through which increasedarea of opening radiant heat cannot pass from the flame into the sleeve42. Spider arms 45 extend inwardly from this skirt portion 44 to acentral mounting boss 46 which slips over the oil pipe or from thecombustion chamber back to the nozzle tip. The construction is analogousto a Venetian blind or overlapping vane effect for permitting a largevolume of air to flow through the shield, but without aflording anystraight line paths which would enable radiant heat to reach the nozzletip. In the preferred construction of such embodiment, the shieldcomprises a short cylindrical member 33, preferably composed of tubing,and a plurality of vanes 31 mounted in staggered or offset relationacross the front end of this cylindrical section. The latter end isformed with a series of notches 3B occurring around the entire tube andinclined in the relation of saw teeth. The vanes 3'! are individualstampings of segmental form, having their narrow ends cylindricallynotched or rounded out, as indicated at 39, so as to form the centralaperture 3| of the shield when the vanes are all assembled over the endof the cylindrical section. This assembly of the vanes is preferablyeffected by welding the rounded outer edges of the vanes to the outerfaces of the notches 3B. The vanes are preferably of sufficient width sothat the edges of adjacent vanes will overlap the requisite amount toprevent radiant heat from the flame or from the combustion spacereaching the nozzle tip [8, this overlapping relation being indicated indotted lines in Figure 4. The arm 29' and U-shaped spring clamp 35'extend from the front portion of the shield in substantially the samerelation described of the arm 29 and clamp 30 in Figure 1, being eitherformed integral with the cylindrical section 36, or in the form of aseparate stamping which is welded or riveted to said cylindricalsection. This embodiment of heat shield is assembled over the nozzle inthe same relation described above, and performs the similar function ofpreventing radiant heat from the flame or from the combustion space fromreaching the nozzle tip. The relatively large aggregate area of theopenings between the staggered vanes enables a large volume of air to becirculated through the shield. It will be noted that the inclineddisposal of the vanes 31 results in a helical or spiral twist beingimparted to the air flowing through the shield. In many instances, theair deflector ring I5 is provided with inclined deflecting vanes 15 forimparting a helical motion to the main body of air discharged throughsaid deflector ring. These inclined vanes I5 may be employed inconnection with either of the embodiments illustrated in Figure l or 3,and when employed in connection with the embodiment of Figure 3 thevanes 15 and 3! are preferably arranged to have the same direction ofinclination, so that the helical motion imparted to the air will be inthe same direction for both the deflector ring and the heat shield.

The embodiment illustrated in Figures 6 and 7 is in the form of acombination nozzle shield and electrode supporting bracket. It comprisesa relatively long sleeve 42 provided with an end cap or end head 43,this unit enveloping the entire nozzle body I! and also the outerportion of the oil pipe It. A flaring skirt portion 44 at the oppositeend of the sleeve 42 deflects an added amount of air from the draft tubel4 I6 and is rigidly secured thereto by the set screw 41. It will benoted that the entire forward portion of the sleeve 42 and the end cap43 are spaced entirely out of contact with the nozzle I1 and nozzlesupply pipe I6, and that the spider structure 45 is the only supportingmeans capable of conducting heat from the heat shield to the nozzle.This supporting structure is spaced so far to the rear of the nozzlehead that the heat must travel a considerable distance along the shieldto reach the spider structure, and this travel is in opposition to thecooling flow of air traveling in contact with the heat shield. Theresult is that very little heat reaches the spider structure. As bestshown in Figure '7, electrode supporting arms 5l5i project outwardlyfrom the sleeve 42, and are formed with bifurcated outer ends foreffecting clamped engagement over the insulating sleeves 23 of theelectrodes. Screws 5252 pass through the bifurcated ends of these armsfor clamping the latter over the electrode sleeves. A third arm 54 alsoextends from the heat shielding sleeve 42 for engaging with the innersurface of the draft pipe I4, whereby to center the sleeve 42 and burnernozzle Within said draft pipe. The electrode supporting arms 5l-5I andthe third arm 54 function as heat dissipating surfaces for dissipatingheat from the rear portion of the heat shield.

The heat shielding end head 43 may be formed integrally with the sleeve42, or may be in the form of a separate sheet metal stamping, asillustrated. I preferably make it of stainless steel, and apply a highpolish to the outer surface thereof, as previously described inconnection with Figures 1 and 2.v The inner edge of said end cap isformed with an inwardly crimped bead 56 adapted to snap into an annulargroove 51 formed in the outer .end of the sleeve 42. At one point aroundthe sleeve there is formed a longitudinally deeper recess 58 forreceiving the bit end of a screwdriver, by the rotation of which the cap43 can be forced off the end of the sleeve 42. The aperture 6| in theremovable head member 43 is preferably so proportioned that the entireconical discharge 32 from the nozzle orifice l9 just clears the edge ofthis aperture 6|, as previously described in connection'vvith Figure I.Said end cap is spaced axially from the nozzle tip I8 so as to leave anair passageway 63 between the end cap or shield and the nozzle tip. Theoperation of this embodiment will be readily understood from thedescription of the preceding embodiments. A greater degree of thermalshielding is obtained by employing the sleeve 42 to envelop the entirenozzle and adjacent portion of the oil supply pipe.

The embodiment illustrated in Figure 8 employs the same construction andarrangement of thermally insulating sleeve 42, but in lieu of the endhead 43 of Figure 6 it employs an end head or shield portion 65 which issubstantially the same as that illustrated in Figures 3, 4 and 5. Thatis to say, it comprises a tubular portion 66, and a plurality of vanes61 mounted in staggered or offset relation across the front end of thistubular section, in substantially the same relation as the tubularmember 35 and vanes 31. The other edge of this tubular section is formedwith an inwardly crimped bead H which is adapted to snap into theannular groove 51 formed in theouterhend of the sleeve.

In either of the two embodiments illustrated in .Figures 6 and 8, theair deflector ring l5 maybe provided with inclined deflecting vanes l5,and

when employed in connectionwith the embodiment of Figure 8 the vanes l5and 61 are preferably arranged to have the same direction ofinclination. If desired, anyone of the embodiments illustrated inFigures 1, 3, 6 and 8 may be arranged so that the heat shield has directmounting attachment or support on this air deflecting ring I5.

While I have illustrated and described What I regard to be the preferredembodiments of my invention, nevertheless it will be understood thatsuch are merely exemplary and that numerous modifications andrearrangements may be made therein without departing from the essence ofthe invention. In this regard, While my invention has its greatest fieldof utility in high pressure burners, nevertheless it also hasadvantageous utility in all nozzle types of burners.

I claim:

.1. In a burner of the class described including a nozzle adapted todischarge liquid fuel under pressure into a combustion chamber, thecombination of a thermally insulating shieldsurrounding said nozzle andoperative to insulate said nozzle from the radiant heat of the flameduring operation of the burner and from the radiant heat of thecombustion chamber following cessation of operation of the burner, saidshield having a substantially central aperture therein aligned with thenozzle orificeforthe'discharge of fuel into the combustion chamber, andhaving secondary apertures for the passage of air through said shield,said secondary apertures being angularly inclined in such relation as toprevent said radiant heat of the flame andof the combustion chamberpassing through said latter apertures and impinging on said nozzle.

2. In a burner of the class described including a'nozzle having anorifice .adapted'todischarge liquid fuel under pressure into acombustion chamber, the combination of a thermally insulating shieldsurrounding said nozzle and operative to insulate saidnozzle from theradiant heat of the flame during operation. of the burner and from theradiant heat of the combustion chamber following cessation of operationof the burner, said shield comprising a cylindrical body portion havingits front end notched in sawtooth profile, vane segments seated in saidnotches in overlapping relation to provide apertures through which aircan pass but through which radiant heat cannot reach said nozzle, and anoil transmitting aperture in said shield aligned with the nozzle orificefor the discharge of fuel into the combustion chamber.

.3. .In a liquidfuelburner comprising an air duct adapted to dischargeair into a combustion chamber and a nozzle Within said air duct adaptedto discharge liquid fuel under pressure into saidcombustion chamber,the. combination of a heat shield surrounding said nozzle for shieldingthe latter from the radiant heat of thefiame during operation of theburner and from the radiant heat of the combustion chamber followingcessation of operation oi the burner, said heat shield comprising arelatively long tubular casting surrounding said nozzlein spacedrelation thereto to define an air passageway therearound, asheet metalend head mounted on the front end of said tubularcasting in position .tosubstantially: enclose; and. shieldsaid; nozzle; from the radiant heatemanatingfrom either of said sources, said-end head having=an=aperturetherein through which the liquid'f-uel 'dischargefrom saidnozzle occurs,aspider-at' the rear end of said tubular casting for maintaining saidnozzle and tubular casting in:radially-spaced relation, said end'headand the-forward-portion of said tubular'casting being spaced entirelyout of 'heat conducting contact with said nozzle-to minimize theconduction of heat'to thelatter, said tubular casting having an annulargroove around its outer-end, and said end head -having an annular beadformed around the inner end thereof for releasably engaging in-saidgroove. V

4. In a liquid fuel burner comprising an air duct adapted to'dischargeair into a combustion chamber and a nozzle within said air ductadaptedto discharge liquid fuel under pressure into said combustionchamber, the combination of a heat shield surrounding said nozzle forshielding the latter from the radiant heat of thefiame during operationof the burner and from the radiant heat of the combustion chamberfollowing cessation of operation of the burner, said heat shieldcomprising a relatively long sleeve front 'endof said sleeve memberinposition to substantially enclose and shieldsaid nozz1e=from theradiant heat emanating from either ;of said sources, said endhead-member having an aperture therein through which the liquid fueldischarge 'from said nozzle occurs, a spider at the rear end of saidsleeve for maintaining said nozzle'and sleeve in-radiallyspacedrelation, said end head member and the forward portion of said sleevebeing spaced outofyheatconducting contact with said nozzle to minimizethe conduction of heat to thelatter and means for'relea sably couplingsaid head ;member ;to said sleeve member, comprising an annulargrooveformed around the outer end of said sleevemember, and an'annular beadformed around the ;inner end of said head member forreleasablyengaging-in saidgroove.

5. In a liquid fuelburner comprising'an air duct adapted to dischargeair'into a combustion chamber and a nozzle within said air ductjadaptedto discharge liquid -fuelunderpressureinto said combustionchambenthe-combination of a heat shield surroundingsaid nozzle forshielding the latter from'the radiantheat of thefiame during operationof the burnerandfrom the radiant heat'of the combustion chamberfollowing cessation of operation of the burner," said heat shieldcomprising a -relatively long sleeve surrounding said nozzle inspaced;relation thereto to define an air passageway' therearound, an endhead-mounted on the front-end of'said sleeve inposition to substantiallyenclose and :shield said'nozzle from the radiant heat emanating fromeither of saidsou'rces, said end head ,hav-f chamber, and a nozzlemember comprising a nozzle supply pipe and a nozzle head adapted todischarge liquid fuel under pressure into said combustion chamber, thecombination of a heat shield surrounding said nozzle member forshielding the latter from the radiant heat of the flame during operationof the burner, and from the radiant heat of the combustion chamber uponcessation of operation of the burner, said heat shield comprising arelatively long sleeve surrounding said nozzle member in spaced relationthereto to define an air passage therearound, and an end head mounted onthe front end of said sleeve in position to substantially enclose andshield said nozzle member from the radiant heat emanating from either ofsaid sources, a spider at the rear end of said sleeve for maintainingsaid nozzle member and sleeve in radially spaced relation, said end headand the forward portion of said sleeve being spaced out of heatconducting contact with said nozzle member to minimize the conduction ofheat to the latter, said sleeve having an annular groove around itsouter end, an annular bead formed around the inner end of said end headreleasably engaging in said groove, said end head having its frontportion notched in saw-tooth profile, and vane segments seated in saidnotches in overlapping relation to provide apertures through which aircan pass but through which radiant heat cannot reach said nozzle member.

7. In a liquid fuel burner comprising an air duct adapted to dischargeair into a combustion chamber, and a nozzle member comprising a nozzlesupply pipe and a nozzle head adapted to discharge liquid fuel underpressure into said combustion chamber, the combination of a heat shieldsurrounding said nozzle member for shielding the latter from the radiantheat of the flame during operation of the burner, and from the radiantheat of the combustion chamber upon cessation of operation of theburner, said heat shield comprising a relatively long sleeve surroundingsaid nozzle member in spaced relation thereto to define an air passagetherearound, and an end head mounted on the front end of said sleeve inposition to substantially enclose and shield said nozzle member from theradiant heat emanating from either of said sources, a spider at the rearend of said sleeve for maintaining said nozzle member and sleeve inradially spaced relation, said end head and the forward portion of saidsleeve being spaced out of heat conducting contact with said nozzlemember to minimize the conduction of heat to the latter, said end headhaving its front portion notched in saw-tooth profile, and Vane segmentsseated in said notches in overlapping relation to provide aperturesthrough which air can pass but through which radiant heat cannot reachsaid nozzle member.

8. In a liquid fuel burner comprising an air duct adapted to dischargeair into a combustion chamber, and a nozzle member comprising a nozzlesupply pipe and a nozzle head adapted to discharge liquid fuel underpressure into said combustion chamber, the combination of a heat shieldsurrounding said nozzle member for shielding the latter from the radiantheat of the flame during operation of the burner, and from the radiantheat of the combustion chamber immediately after stopping the operationof the burner, said heat shield comprising a supporting casting attachedto said nozzle supply pipe at a point to the rear of said nozzle head,and a sheet metal end head mounted on said supporting casting inposition to substantially enclose and shield said nozzle member from theradiant heat emanating from either of said sources, said supportingcasting having an annular seating surface,

said sheet metal end head having a cooperating annular seating surfacefor releasably engaging the seating surface on said casting, said heatshield being supported entirely out of contact with said nozzle supplypipe and nozzle head except at said point of attachment of saidsupporting casting on said nozzle supply pipe, whereby to minimize theconduction of heat from said heat shield to said nozzle head, the frontof said end head being of substantially semi-spherical formation andhaving an aperture through which the liquid fuel discharge from saidnozzle occurs, said aperture having a diameter less than half thediameter of said nozzle head whereby said end head shields the majorfrontal area of said nozzle head from radiant heat. f

9. In a liquid fuel burner comprising a draf tube adapted to dischargeair into a combustion chamber, and a nozzle member comprising a nozzlesupply pipe and a nozzle head having an orifice adapted to dischargeliquid fuel under pressure longitudinally of said draft tube into saidcombustion chamber, the combination of a diately following cessation ofoperation of the burner, the outer surfaces of said heat shield beingcooled by the outer stream of air flowing through said draft tube, saidheat shield comprising a supporting casting surrounding said nozzlemember, and a sheet metal end head mounted on said supporting casting inposition to substantially enclose and shield said nozzle member from theradiant heat emanting from either of said sources, said end head beingsupported in spaced relation to said nozzle member to permit air flowtherebetween, means for detachably connecting said end head to saidsupporting casting the front of said end head having a relatively smallaperture through which the liquid fuel discharge from said nozzleoccurs, said aperture having a diameter less than half the diameter ofsaid nozzle head whereby said end head shields the major frontal area ofsaid nozzle head from said radiant heat.

10. In a liquid fuel burner comprising a draft tube adapted to dischargeair into a combustion chamber, and a nozzle member comprising a nozzlesupply pipe and a nozzle head having an orifice adapted to dischargeliquid fuel under pressure longitudinally of said draft tube into saidcombustion chamber, said nozzle head being of relatively small size andcomprising an outer portion inclined inwardly toward said nozzle orificethe combination of a heat shield surrounding said nozzle head forshielding the latter from the radiant heat of the flame during operationof the burner, and from the radiant heat of the combustion chamberimmediately following cessation of operation of the burner, said heatshield comprising a heat reflecting shell enveloping said nozzle head inspaced relation thereto to define a passage for a cooling flow of airtherebetween, and mounting means associated with the rear portion ofsaid reflecting shell for: supporting-t the. latter. in: such relation las to. conduct .a minimum amount of heat from saidreflecting-shellitosaidlnozzle member, said! reflecting shell extending acrossthefrontsurface of .said nozzle head and/having a relatively restricted.aperture therein through which the.- liquidlfuel .is ,discharged ,fromsaid nozzle 7 head andQthrough which said coolingflow, of airisdischarged, the outer-portion of saidlrefiecting shell jextendinginwardly at. almore acute angle thancthetouter portion of saidnozzleflhead so as to dispose the planeofvsaid aperture in closeproximity to..the .plane of .the. nozzlerorifice, and the, diameter ofsaid aperturepbeing much .less than the. diameter .ofmsaid .nozzle head,whereby said passages. for. conducting cooling air dimin-.

ishes in effective area adjacent .to said apertureto accelerate theflow-chair. through said, aperture, and; whereby; said i.reflectingshellshields.-

the major frontal .area of .said nozzlerheadrfr'om the radiant heat.'.of ,the flame.v and f the. come bustion chamber.

11. In a liquidifuel burnercomprising. an air duct vadapted 'todischargeQair. into a combustion chamber, and a, nozzle membercomprising a nozzle supply pipe and'a. nozzlehead engaging over the endof 'saidsupplypipe and having an orifice discharging liquid 'fuel underpressure into said combustion chamber, ,thecombination ofa heat shieldsurroundingsaid nozzlev member for shielding the latter from the radiantheat'of. the flame during operation of "the burner and from.

the radiant heat of the combustion chamberimmediately after stopping theoperationof the burner, said (heat shield comprising a mounting memberand'an end'headrcarried thereby, said mounting member being mounted onsaid nozzle.

supply pipe at a point substantially in rear ofsaid nozzle head, meansfor detachably securing said end head to said mounting member,.said ,end

headsubstantially enclosing and shielding, said. nozzlemember from theradiant heat emanating: from either. of said sources and beingsupported.

in spacedvrelation to saidnozzleshead to permit a coolingfiow of airtherebetween, the entireheat shield beingsupported out of contact withsaidnozzlev supply pipe and .nozzle head except at saidpoint ofmounting-0f said mounting member on said nozz1e.,supply pipe in rearofsaid nozzle head said end head having an aperture'in.

its vfront end through whichthe liquid fuel discharge from the nozzleorifice occursand through which said cooling flow of .air canralsodischarge, said aperture beingof relatively small size where-- bytheentire conical discharge from the nozzle orifice just clearsthe..edge of theaperture. and.

' nozzlefrom. the radiant heat of the flame dur- 2E ing operation of theburner and from theradiant heatofthe combustion chamber immediatelyafterstoppingthe operation of the burner, said shield comprising acastrmetal sleeve enveloping said'nozzle, and a removable sheet metalend cap mounted on said sleeve,.said sleeve; and said cap being spacedfrom said nozzle and being substantially out of heat conducting relationto said nozzle, said .end caplhaving an aperture therein adaptedEtolalign with the orifice innsaid nozzle; the aperture in saidlcapbeingrelatively small whereby the entire'conical discharge of liquidfuel'from the nozzle orifice-just clears said aperture and whereby themajor portion of said nozzle is protected. from radiant heat.

WILLIAM F. KLOCKAU.

